The weft thread insertion in conventional air weaving looms takes place through one or several main nozzles, whereby each main nozzle is coordinated with one yarn. The main nozzles are arranged in bundles and so centered on the air insertion channel that each time one yarn can be carried into the air insertion channel.
The yarn is transported through the weft thread insertion air channel in that an air guiding of the weft thread through the insertion air channel takes place by means of relay nozzles arranged in a row along the insertion air channel through the weaving reed.
Heretofore, the relay nozzles have been controlled in sequence in an impulse type manner, so that the thread tip was seized by the air stream for pulling the thread through the insertion air channel.
It has been a disadvantage in conventional controls of the relay nozzles in air weaving looms that the impulse duration of the control of the relay nozzles had to be adjusted to the thickest thread which is least air effective. It was necessary to take care that the heaviest thread was still sufficiently exposed along its length to the air flow, so that even the thickest thread achieved the speed sufficient for its transport through the insertion air channel. Supplying air in accordance with the requirements of the heaviest thread has the disadvantage that, if less heavy yarns are simultaneously woven, these lighter more air effective yarns receive too much air, whereby the excess air is wasted. On the one hand, the wasted air caused a disadvantageously high air consumption and, on the other hand, it involved the danger of damaging the yarn. In bad cases it was no longer possible to weave substantially different yarns into the same fabric.